RESEARCH ARTICLE Challenges and Advances in Development of Active Components to Modify Headspace Gases in Packaging of Fresh Produce and Muscle Foods PREFACE API 2015 Ziynet Boz Bruce A. Welt* University of Florida University of Florida Jeffrey K. Brecht William Pelletier University of Florida University of Florida Eric McLamore Greg Kiker University of Florida University of Florida Jason E. Butler University of Florida ABSTRACT Modified Atmosphere Packaging (MAP) has been widely used as an effective way to preserve foods. Fresh produce, meat and meat products, seafood, and dairy products can benefit from modified gaseous atmospheres, which are usually achieved by reducing oxygen and increasing carbon dioxide concentrations, within limits, defined by product tolerances. MAP of fresh produce is particularly challenging because products are living and respiring. Respiration rates depend on several factors including temperature, oxygen, and carbon dioxide concentrations. Balancing package permeation with respiration is challenging, often due to limited selection of practical packaging materials. Failing to remain within tolerance limits of products leads to rapid quality loss. Gas barrier properties of packages determined rate of gas exchange with the external environment and is a critical factor for achieving tolerable levels. Availability of packaging materials that meet requirement of specific produce is essential. Relative permeability of common films to carbon dioxide is about 3 to 6 times of that to oxygen, often leading to package collapse for package atmospheres that benefit from carbon dioxide. Films often fail to provide desired oxygen transmission rates, high carbon dioxide to oxygen selectivity and desired mechanical properties simultaneously. Despite advances, minimal availability and high cost of selective barrier films limit applications of MAP for fresh produce packaging. Therefore, active packaging components and films are being developed and designed to overcome these limitations. Inserts or films that contain active mixtures as gas emitters Challenges and Advances in Development of Active Components 62 RESEARCH ARTICLE and/or scavengers are now commercially available. “Clean label” trends are motivating alternative approaches using active packaging components. KEY WORDS modified atmosphere packaging, MAP, food, muscle, fresh, produce, respiring, respiration, active packaging PREFACE API 2015 *Bruce A. Welt Corresponding Author [email protected] INTRODUCTION ergonomic and aesthetic designs. Technologies such as active and intelligent packaging have been The food industry has been shaped by changing proposed, but have not yet been fully realized com- consumer demands and availability of a wide variety mercially [7]. Modified atmosphere packaging of foods. Past decades have witnessed the increased (MAP) can provide benefits by slowing deteriora- consumption of products with proven advantages tive reactions. Sales volumes of advanced packag- to human health and well-being. Fruits and veg- ing technologies and MAP continue to grow and etables were demonstrated to have health benefits are anticipated to reach $6.4 billion by 2020 [8]. against chronic disease and cancer [1]. Fish and One of the most challenging aspects of MAP is the lean red meats provide essential macro and micro- unique atmospheric requirements for the variety of nutrients [2], [3]. Muscle food products remain the products. In red meats, oxygen is necessary for the main source of protein and nutrients [4]. Accel- bright red color expected by consumers, but oxygen erating consumption of fresh produce, meat and also contributes to degradative oxidation. There- fish has led to improved post-harvest/post-mortem fore, techniques to control oxygen exposure are of handling, processing, packaging, transportation, value to red meat products. Respiring fresh produce and retail practices. However, the perishable and require distinct levels of oxygen and carbon dioxide. variable aspect of natural, high-value products con- Typically, oxygen levels lower than atmospheric tinues to challenge industry to develop methods to and carbon dioxide higher than atmospheric are preserve “freshness” without compromising safety. needed. Great care is required to ensure that oxygen Improved preservation could mitigate loss of nearly is not reduced to levels that result in anaerobic res- one-third of foods produced [5]. Recent consumer piration. For fish, the primary goal of MAP is pre- preferences for minimally processed foods and venting microbial growth. Relatively high carbon overall “freshness” have led marketing efforts to dioxide levels help to reduce pH via equilibrium switch focus from “shelf life extension” to “pres- of the dissolved gas with carbonic acid. Therefore, ervation of preferred quality” Although shelf life is flushing packages with carbon dioxide as high as an important parameter, the main selling factor is 100% by volume may prove useful [9]. quality as perceived by the consumers [6]. Elevated carbon dioxide concentrations are Packaging innovations have been mainly often desirable in packaged foods anti-microbial limited to barrier modifications as well as improved effects, regardless of product type. Carbon dioxide is Journal of Applied Packaging Research 63 soluble in aqueous solutions, food tissues and packag- The European Commission Regulation (EC) ing materials. Rate of permeation of carbon dioxide No 450/2009 on active packaging defines active through polymers is three to seven times greater than materials as “Materials and articles that are for oxygen [10]–[12]. A comprehensive review on O2/ intended to extend the shelf-life or to maintain or CO2 diffusivity and solubility in a variety of foods and improve the condition of packaged food; they are polymers was written by Chaix et al. [13]. designed to deliberately incorporate components Loss of gas from packages combined with sol- that would release or absorb substances into or ubility of headspace gases in packaged products from the packaged food or the environment sur- causes reductions in volume in flexible packaging, rounding the food can aid overcoming product- resulting in unattractive, deflated packages that may specific challenges”. Thus, active packaging is con- appear to be less than “fresh” [10], [14]–[16]. Defla- sidered a secondary level of packaging, but may tion [17] causes misconceptions about defects related play a role in primary functions, such as modified to products and/or packaging, such as inferior pack- atmosphere [19]. Gas emitting or scavenging via aging materials or methods, microbiological activity active components comprises a significant portion or seal defects. Industry recognizes package volume of active packaging. Adjustment of package gas changes as a problem and works to mitigate the requires knowledge of effects on biochemical pro- problem by adjusting initial volumes of headspace cesses, physical interactions, microbial flora [20], gases and by considering shipping distances [18]. and other variabilities. MAP and AP applications Understanding the distinct atmospheric may be justified based upon value-added consumer requirements of foods drives research, process- convenience, new product opportunities that did not ing and packaging innovation. MAP advances otherwise exist, branding opportunities, extended have been realized in mathematical modeling and maintenance of quality, reduced waste, and/or computer simulation, materials development and higher margins. Increasingly, due to regulatory properties analysis and measurement and gas gen- and/or consumer preference, chemical preserva- eration, mixing and handling. Modified package tives cannot be added in certain foods or package atmospheres may be obtained actively or passively. materials. For this reason, vacuum packaging, due “Active” MAP involves injection of the desired to its simplicity and effectiveness, remains partic- atmosphere into packages so as to instantly arrive ularly important [21]. For example, a recent trend at the targeted atmosphere. “Passive” MAP relies of “clean-label” products creates an opportunity for upon interactions among product (e.g. product res- food preservation through MAP and AP by elimi- piration rate), package (i.e. gas transmission rates) nating artificial food-additives [22]. and the environment (i.e. ambient gas composition and temperature) to arrive at target atmospheres MAP AND PRODUCT CONSIDER- sometime after packaging. Often, optimal modified ATIONS atmospheres cannot be attained using commercially available packaging materials and/or gas flushing. For example, due to differences in permeation rates Map Considerations for Fresh Produce of gases, we may be able to achieve the desired level Biological activity in fresh produce continues for oxygen or carbon dioxide, but not both at the after detachment from the plant. Harvested produce same time. Additionally, carbon dioxide emitters draws resources from its own stores causing degra- may be used to prevent package collapse. dation. Deterioration rate is influenced by respiration Challenges and Advances in Development of Active Components 64 rate, ethylene sensitivity and exposure, genetics, Oxygen serves as final electron acceptor in physical injuries, microbiological activity and physi- aerobic respiration reactions [35]. The typical goal ological disorders [23]. Generally, reduction of respi- of MAP is to reduce oxygen to the lowest possible ration rate is the primary objective of MAP for fresh level that supports